Because google has a decent interface to access them? Sure, I could use terraserver (and get nagged for money to get anything of decent resolution) or USGS, after I take a course on GIS to understand all of the bloody terminology.

While the White House itself doesn't on a grand scale the roof, and the buildings (OEOB and Treasury Dept?) on either side, which might have very interesting stuff on their roofs, do appear to have been "enhanced" for your protection.

That above URL is in the middle of NTS. If you move down, you see this really light-colored triangle splotch. That's the dry lake that houses the Yucca air strip in Area 6. Area 3 is the piece above it with the brunt of the craters.

Most of those out there are collapsed sinkholes from underground testing. The most famous crater, Sedan, is up in Area 10. It's also interesting to see that what look like entire little cities that were built just for testing are sitting around abandoned. Oh, also a lot of what look like craters in Area 3 are really storage holes for the Radioactive Waste Management Site. They used to fill them with hot dirt and other junk from tests, but now they're filling them with other DoD hazardous waste.

As have been mentioned before, yes, it's an optical illusion. Compare this (rather famous test) to this.

Also in the same general area: Hawthorne, NV, home of one of the largest munition dumps in the world. Each one of those little bumps is an entrance to enough obsolete ammo to run your own personal war.